1. Field of the Invention
This invention relates to a power-supply control apparatus. More particularly, it relates to an apparatus that uses a battery or the like to provide a main power supply. The apparatus is designed for use in, for example, apparatuses for locking and unlocking the doors of automobiles.
2. Description of the Related Art
In conventional apparatuses that use a battery, providing a main power supply and a backup power supply required for controlling the apparatus, the main power supply is turned off in the standby mode in order to save the battery power. Such an apparatus comprises a signal-detecting circuit and a control circuit. The signal-detecting circuit detects a signal that changes the operating mode back to the operation mode from the standby mode to the operation mode. The control circuit activates the main power supply. In the standby mode, both circuits are driven by the backup power supply generated from the battery power supply. Hence, the battery power must be consumed in the standby mode.
A conventional power-supply control apparatus used in apparatuses that lock and unlock the doors of automobiles will be described in detail.
To get into a car, the user first inserts the key into the key slot in the door beside the driver's seat. When the user turns the key, the door-lock motor is driven, unlocking that door. The doors can therefore be opened.
When the door is thus unlocked, the engine remains stopped. So does the generator. Thus the battery is used to drive the motor-lock motor to open the door without supply of an electric current from the generator. The battery is used to drive the door-unlock motor to open the door. Inevitably, the battery power is consumed.
Moreover, power is always supplied from the backup power supply to the signal-detecting circuit so that the circuit may detect a signal for changing the operating mode back to the operation mode from the standby mode to the operation mode, no matter when the signal comes. Also, power is always supplied from the backup power supply to the door-unlock motor control circuit. Hence, the battery power is consumed even when the door-unlock motor is not driven to open the door.
Recently, intra-vehicle LAN (Local Area Network) and the like come into common use. The consumption of the battery power inevitably increases. This is a great problem.
As described above, the conventional apparatus that locks and unlocks the doors of automobiles fast consumes the battery power when the door-unlock motor is driven to open the doors, when the signal detecting circuit operates before the doors are open and when a circuit operates to control the door-unlock motor.